Liquid sample loader for analytical instruments and method of loading same

ABSTRACT

A liquid sample loader for an analytical instrument includes a sample holder with a sample well for holding a liquid sample and a sample passageway extending upwardly at an inclined angle from a bottom portion of the well, a pump positioned upstream from the sample holder and an upstream passageway coupled between the sample and the pump. A controller controls the pump to push the sample in the sample well downstream through the sample passageway toward the measuring instrument.

TECHNICAL FIELD

This invention relates to analytical instruments, and in particular,liquid sample loaders for use with the analytical instruments.

BACKGROUND OF THE INVENTION

Liquid sample loaders are used to load samples into an analyticalinstrument for measuring various properties of the sample. Examples ofanalytical instruments are polarimeters for measuring the opticalrotation of samples and refractometers for measuring the refractiveindex of samples.

Often, a laboratory worker loads the analytical instrument manually byinjecting the liquid sample into the input port of the instrument with asyringe while watching for excess sample to appear at the output port toverify that the instrument is fully loaded. A tube connected to theoutput port carries any excess sample to a waste jar.

Once measurements are made by the analytical instrument, the liquidsample is removed. First, the syringe is removed from the input port.Then, one end of a flexible hose with the other end connected to an airpump is attached to the input port. The pump is turned on and the pump'sair pressure pushes the sample in the analytical instrument out throughthe output port and on to the waste jar. To clean the instrument,solvents are injected and removed in a similar manner. Often the finalstep is to dry any residual solvent by leaving the air hose attached andthe pump running for a few minutes.

One disadvantage of the above manual method is the need for a trainedoperator to load and handle syringes. Also, these syringes are cleanedor treated as a disposable consumable which adds a significant cost tothe operation.

At the other end of the spectrum, fully automated liquid sample loaderscan be used. In those devices, liquid samples are placed in vials ortest tubes in motor driven racks. A robotic needle enters the liquidsample and draws it into the analytical instrument by suction. A lightgate/sensor, which is an optical method of detecting the presence of theliquid sample in a transparent tube, is placed near the exit port of theanalytical instrument to detect when the loading is complete. Keepingthe light gate as close to the exit port as possible minimizes thevolume of liquid sample required for each analysis. Cleaning solventsstored in tanks, a system of valves, and an air pump are used to cleanand dry the instrument.

While the fully automated loaders offer the convenience of unattendedoperation, there are many disadvantages such as high cost, highmaintenance, and larger size of the equipment, as well as the need toload and clean or dispose of the vials.

In between the above two types of loaders, there are semi-automatedloaders for loading samples into the analytical instruments. One suchloader is disclosed in U.S. Pat. No. 4,827,746 issued to Kawaguchi,which is incorporated herein by reference and is shown in FIG. 1.

A U-shaped thin oscillating tube 1, which is a part of the analyticalinstrument is supported by a supporter P. A magnet 2 is attached to tube1 at the bottom of the U-shape, and oscillates together with the tube. Adetection signal, which is an electric signal indicative of theoscillation of magnet 2, is generated by a detection head 3. The densityof the liquid which fills tube 1 is calculated on the basis of thedetection signal by a detection circuit (not shown). The detectionsignal is also utilized to drive oscillating tube 1 by driving head 4.One end of tube 1 is open via a sampling tube 5 in a vessel 6 in whichthe liquid is supplied. The liquid is introduced into tube 1 by a pump9, which is connected to the other end of tube 1 through a valve 7 andanother vessel 8.

In particular, the bottom end of sampling tube 5 draws a liquid samplefrom vessel 6 by suction from the pump 9. The solenoid valve 7 is closedwhen the loading is complete to prevent the sample from syphoning backinto the vessel 6 during analysis.

While the sample loader of the above type is relatively easy to use andhas a moderate cost, there are many disadvantages. First, because thesample is drawn by suction, it may not be able to handle high viscositysamples due to higher forces required or samples with components whichmay separate and evaporate under suction. While the 746 patent doessuggest that the above method could be modified by using pressure, thereis no discussion of how this can be achieved. Second, disposal orcleaning of the sampling vessel 6 needs to be done manually by removingthe vessel. Third, disposal or cleaning of the outside of the samplingtube 5 needs to be done manually. Fourth, because the solenoid valve 7is in the sample path, it is exposed to various types of samples orrinse solvents. Valves that are inert to every sample or rinse solventthat might be used can be very expensive. Moreover, valves are subjectto damage from particulates and residual material that is allowed to drywithin the valve. Fifth, some wasted sample is always left in the bottomof the sampling vessel 5.

Therefore, it would be desirable to provide an improved sample loaderand method that overcome the disadvantages discussed above.

SUMMARY OF THE DISCLOSURE

A liquid sample loader for an analytical instrument according to oneaspect of the present invention includes a sample holder with a samplewell for holding a liquid sample and a sample passageway extendingupwardly at an inclined angle from a bottom portion of the well, a pumppositioned upstream from the sample holder and an upstream passagewaycoupled between the sample and the pump. The pump pushes the sample inthe sample well downstream through the sample passageway toward themeasuring instrument.

According to another aspect of the present invention, a method ofloading a liquid sample into an analytical instrument is provided. Anoperator inserts a liquid sample into a sample well of a sample holderhaving a sample passageway that extend upwardly at an inclined anglefrom a bottom portion of the sample well. Then, an air pump positionedupstream from the sample holder is turned on to pump air through anupstream passageway into the sample well so as to push the samplethrough the sample passageway toward the analytical instrument. When thesample has been loaded into the analytical instrument, the air pump isturned off.

Advantageously, both the well and the inclined sample passageway fillfrom the bottom under the action of gravity, which displaces airupwards. The upward displacement of air tends to eliminate the formationof slugs of liquid sample separated by trapped air. As a result, theliquid sample travels as a single body. This allows a sample sensorlocated by the analytical instrument to be a reliable indicator that thesample has been loaded fully without trapped air. Also, because theloading operation uses a pressure mode of the air pump to push theliquid sample rather than pull by vacuum, the present invention issuitable for the widest variety of sample types including those withhigh viscosity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sample loader for an analytical instrument according to theprior art.

FIG. 2 illustrates an exemplary sample loader for an analyticalinstrument according to one aspect of the present invention.

FIG. 3 illustrates a sample loader for an analytical instrumentaccording to an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 illustrates an exemplary sample loader 10 for an analyticalinstrument 20 according to one aspect of the present invention. A sampleholder 12 includes a hinged lid 14, sample well 16 for holding thesample liquid and sample passageway/lumen 18 positioned within theholder. Once the liquid sample has been filled in the sample well 16,the hinged lid 14 fluidly seals the well 16. The sample well 16 as shownhas a tapered bottom such as a conical shape and a bottom portion of thewell is in fluid communication with the passageway 18 which extends fromthe bottom portion at a preselected upward inclined angle and has anexit point near the top of the sample well. The shape of the well 16 andthe angle of the passageway 18 ensure that there are no gaps in thesample liquid to cause separate slugs of the liquid sample as it travelsdownstream towards an analytical instrument 20. Although the samplepassageway 18 as shown in FIG. 2 extends from the tapered bottom end, itcan extend from any point in the bottom portion so long as there is nogap in the sample liquid between the well 16 and the passageway to causeany separate slugs of the liquid. The angle of the inclined passageway18 can be as high as 90 degrees from horizontal.

A transfer passageway/tube 22 connected between the top of the samplepassageway 18 and an input port 25 of the analytical instrument 20carries the liquid sample to the instrument. A waste passageway/tube 24is disposed between an output port 26 of the instrument 20 and a wasteholder/jar 28. A sample sensor 30 is located on the waste tube 24 nearthe output port to sense the liquid sample as it exits the analyticalinstrument 20. The sample sensor 30 is located near the output port 26to reduce the waste. In one embodiment, the sample sensor 30 is anoptical sensor (e.g., light emitter and detector) that detects thechange in intensity of light passing through the waste passageway 24.

An upstream passageway/tube 32, which is strategically positionedupstream of the sample well 16, has a first end (upstream end) connectedto an air pump 34 and a second end (downstream end) coupled to thesample well 16 through a through lumen 13 in the hinged lid 14 such thatthe upstream passageway is in fluid communication with a top portion ofthe well where there is no liquid sample. Preferably, the air pump 34has a variable or multi speed capability to allow for a low speedoperation for loading the liquid sample into the analytical instrument20 and a high speed operation for drying the lumens in the liquid pathwhich include the sample passageway 18, transfer tube 22, lumen (notshown) inside the analytical instrument 20 between the input port 25 andexit port 26, and waste tube 24.

A flow control valve 36 controls the flow of air from the air pump 34 tothe sample well 16. A vent passageway/tube 38 is coupled to the upstreampassageway 32 between the flow control valve 36 and the sample holder12. A relief valve 40 is positioned on the vent passageway 38 to relieveany excess air pressure beyond atmospheric pressure in the upstreampassageway 32 into atmosphere. Preferably, the valves 36,40 areelectronically controlled solenoid valves. A controller 42 is connectedto and controls the operation of the air pump 34, flow control valve 36,relief valve 40, and sample sensor 30.

A method of loading and unloading the sample into and from theanalytical instrument 20 will now be described. Initially the air pump34 is off and both valves 36,40 are closed. An operator then raises thehinged lid 14 and pours the liquid sample into the sample well 16. Theoperator closes the hinged lid 14 fluidly sealing the sample well. Theoperator then signals the controller 42 to start the loading operation.Although not shown, the operator could press a button coupled to thecontroller 42 which signals the controller to start the loadingoperation. Alternatively, and also not shown, a switch could be builtinto the sample holder 12 which detects when the lid 14 is closed. Inthat case, the controller 42 can be programmed/configured to keep thepump 34 turned off regardless of the operator's wish until it receivesan indication from the switch that the lid 14 is closed.

The controller 42 opens the flow control valve 36 and then starts theair pump 34. The air pressure of the upstream passageway 32 from thepump 34 forces the liquid sample downward in the well 16, up through theinclined passageway 18, through the transfer passageway 22 into theanalytical instrument 20, then into the waste passageway 24.

The presence of the liquid sample is detected by the sample sensor 30which then transmits a signal to the controller 42 indicating that thesample is present in the waste passageway 24. The controller 42 thenperforms a sequence of steps to stop the loading process. The controllerturns off the air pump 34 and then closes the flow control valve 36. Thecontroller 42 then turns on the relief valve 40 momentarily to releaseany residual pressure in the upstream passageway 32 which wouldotherwise continue to advance the liquid sample. Preferably, the reliefvalve 40 turns on for at least 0.1 second and at most 2 seconds. Mostpreferably, the controller 42 turns on the relief valve 40 for at least0.25 second and at most 1 second.

Advantageously, once the lid 14 is closed, the entire operation of theabove described loading process can be automatically controlled by thecontroller 42.

After the analysis of the liquid sample by the analytical instrument 20is complete, the liquid sample will need to be unloaded. The unloadingoperation includes flushing of the liquid sample from the passageways,and cleaning and drying of the passageways. To do so, the operatorsignals the controller 42 to start the unloading operation. Although notshown, the operator could press a button coupled to the controller 42which signals the controller to start the unloading operation.

In response, the controller 42 opens the flow control valve 36 and thenturns on the air pump 34 which forces the liquid sample into the wastecontainer 28. Preferably, the air pump 34 operates at a higher speedthan during the loading steps since there is no need to be concernedabout forming air bubbles and the higher speed allows the passagewaysand the sample well to be dried faster.

Once the liquid sample stops flowing into the waste container 28,cleaning and drying steps are performed. With the air pump 34 continuingto run, the operator raises the hinged lid 14, pours a cleaning solventinto the sample well 16, and closes the lid to clean the well and thepassageways 18,22,24. These cleaning steps are repeated as needed toremove all residual liquid sample. After the last rinse is loaded, thecontroller 42 keeps the air pump 34 on for a few minutes to dry theentire liquid sample path.

Advantageously, once the unloading process is started, the entireoperation of the above described unloading and cleaning process can beautomatically controlled by the controller 42. Thus, after thecontroller 42 turns on the air pump 34 at the higher speed to blow outthe remaining sample into the waste container 28, the pump continues torun while the operator opens and closes/locks the lid 14 to pourcleaning agent as many times as are needed to clear the samplepassageways. The controller 42 is programmed to continue to run the airpump 34 for a predetermined time period, e.g., 5 minutes, to dry thesample well and the sample passageways, and then turn the pump off.

The conical shape of the sample well 16 and the inclined passageway 18extending at an inclined upward angle from the bottom of the wellprovide many performance benefits. As the operator pours the liquidsample into the well 16, both the well and the inclined samplepassageway 18 fill from the bottom under the action of gravity, whichdisplaces air upwards. The upward displacement of air tends to eliminatethe formation of slugs of liquid sample separated by trapped air. As aresult, the liquid sample travels as a single body. This synergisticallyallows the sample sensor 30 to be a reliable indicator that theanalytical instrument 20 is loaded fully without trapped air.

Another important advantage of the form of the sample well 16 is thatthe entire liquid sample is forced out of the sample well. No liquidsample is left in the well 16 other than a film on the walls. Theability to load essentially the entire liquid sample together with theability to use a sample sensor 30 reliably results in a system 10 thatrequires a minimum volume of sample per analysis. Another importantadvantage of the form of the sample well 16 is that the dip tube such asthe one 5 shown in FIG. 1 has essentially moved inside of the wall ofthe well 16 and as a result, has no outside surface that would requirecleaning.

Another important advantage is that the lid 14 sealing the sample well16, together with the closed valves 36,40, prevents the liquid samplefrom syphoning out of the analytical instrument 20 during analysis. Itis the sealed lid 14 that allows the valves to be placed in the air pathrather than in the liquid sample path.

As a result, the present invention provides an efficient and relativelyinexpensive device for loading a liquid sample into an analyticalinstrument without using syringes, without using disposable consumablesand with using only a minimal volume of the sample liquid. Because theloading operation uses a pressure mode of the air pump to push theliquid sample rather than pull by vacuum, the present invention is alsosuitable for the widest variety of sample types including those withhigh viscosity.

FIG. 3 is an alternative sample loader for an analytical instrument.While the loader is similar to that of FIG. 2, there are somedifferences. In this embodiment, a controller is replaced with a simpleon/off switch 50 which connects to and controls the pump 34. A secondpump comprising a threaded piston 46 and a cylinder 48 is coupled to theupstream passageway 32. Unlike FIG. 2, the sample loader in FIG. 3 doesnot have a sample sensor 30.

In operation, the pump 34 is turned off by the switch 50, valve 36 isclosed and the threaded piston 46 is in a raised position. To load thesample, the user places the liquid sample into the well 16 and closesthe lid 14 to seal the well 16. The user then rotates the threadedpiston 46 inward in cylinder 48 which creates pressure to achieve thedesired fill of the liquid sample into the analytical instrument 20.

Once measurements are made by the analytical instrument 20, a cleaningoperation needs to be performed. The user actuates the switch 50 to openthe flow control valve 36 and turn on the pump 34 to blow out the liquidsample in the well 16 and all the passageways downstream of the well.Cleaning solvents are then loaded in the well 16 and pushed through withthe air pump 34 in a similar manner as the liquid sample.

The advantages of this arrangement are simplicity and lower cost as thesample sensor 30 is eliminated and controller 42 is replaced with asimple switch. Moreover, very fine control of the sample loading can beachieved through the rotation of the threaded piston 46.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

What is claimed is:
 1. A method of loading a liquid sample into ananalytical instrument comprising: inserting a liquid sample into asample well contained within a sample holder, the sample well having abottom portion in communication with an upwardly inclined angle portionof a sample passageway disposed within the sample holder and outside thesample well; turning on an air pump positioned upstream from the sampleholder to pump air through an upstream passageway into the sample wellconfigured to push a portion of the sample out of the bottom portion ofthe sample well and into the upwardly inclined angle portion of thesample passageway toward the analytical instrument; turning off the airpump when the sample has been loaded into the analytical instrument. 2.The method of claim 1, wherein a controller automatically controls theair pump.
 3. The method of claim 2, further comprising: continuouslyreceiving by the controller a signal from a sample sensor located nearan output port of the analytical instrument; wherein the step of turningoff the air pump includes sending a turn-off signal by the controller tothe air pump when the signal from the sample sensor indicates thepresence of the sample.
 4. The method of claim 1, wherein the sampleholder includes a hinged lid, the method further comprising closing thehinged lid to fluidly seal the sample well.
 5. The method of claim 1,further comprising: under the control of a controller, turning on a flowcontrol valve positioned in the upstream passageway during the loadingof the liquid sample into the analytical instrument; and turning off theflow control valve when the sample has been loaded.
 6. The method ofclaim 5, after the flow control valve is turned off and under thecontrol of the controller, further comprising opening a relief valvepositioned in the upstream passageway between the flow control valve andthe sample holder for a period between 0.1 and 2.0 seconds to releaseresidual air pressure in the upstream passageway into the atmosphere. 7.The method of claim 5, further comprising: after inserting the liquidsample into the sample well, closing a hinged lid to fluidly seal thesample well; continuously receiving a signal from a sample sensorlocated near an output port of the analytical instrument; wherein whenthe signal indicates the presence of the sample, the air pump is turnedoff; turning off a flow control valve positioned in the upstreampassageway; opening a relief valve positioned in the upstream passagewaybetween the flow control valve and the sample holder for a periodbetween 0.1 and 2.0 seconds to release residual air pressure in theupstream passageway into the atmosphere.
 8. The method of claim 5,wherein the sample holder includes a lid for fluidly sealing the samplewell and for receiving the upstream passageway such that the upstreampassageway is in fluid communication with the sample well through thelid when the lid is closed, the method further comprising: under thecontrol of a controller, turning on a flow control valve positioned inthe upstream passageway to push the liquid sample out of the sample wellthrough the sample passageway; and turning off the flow control valvewhen the sample has been removed from the sample well.
 9. A method ofloading a liquid sample into an analytical instrument comprising:inserting a liquid sample into a sample well of a sample holder having asample passageway extending upwardly at an inclined angle from a bottomportion of the sample well; turning on an air pump positioned upstreamfrom the sample holder to pump air through an upstream passageway intothe sample well configured to push the sample through the samplepassageway toward the analytical instrument; turning off the air pumpwhen the sample has been loaded into the analytical instrument; underthe control of a controller, turning on a flow control valve positionedin the upstream passageway during the loading of the liquid sample intothe analytical instrument, and turning off the flow control valve whenthe sample has been loaded; and after the flow control valve is turnedoff and under the control of the controller, opening a relief valvepositioned in the upstream passageway between the flow control valve andthe sample holder for a period between 0.1 and 2.0 seconds to releaseresidual air pressure in the upstream passageway into the atmosphere.10. A method of loading a liquid sample into an analytical instrumentcomprising: inserting a liquid sample into a sample well of a sampleholder having a sample passageway extending upwardly at an inclinedangle from a bottom portion of the sample well; turning on an air pumppositioned upstream from the sample holder to pump air through anupstream passageway into the sample well configured to push the samplethrough the sample passageway toward the analytical instrument; turningoff the air pump when the sample has been loaded into the analyticalinstrument; under the control of a controller, turning on a flow controlvalve positioned in the upstream passageway during the loading of theliquid sample into the analytical instrument, and turning off the flowcontrol valve when the sample has been loaded; after inserting theliquid sample into the sample well, closing a hinged lid to fluidly sealthe sample well; continuously receiving a signal from a sample sensorlocated near an output port of the analytical instrument; wherein whenthe signal indicates the presence of the sample, the air pump is turnedoff; turning off a flow control valve positioned in the upstreampassageway; and opening a relief valve positioned in the upstreampassageway between the flow control valve and the sample holder for aperiod between 0.1 and 2.0 seconds to release residual air pressure inthe upstream passageway into the atmosphere.